Packer transmission service has been in use for some time and has traditionally been employed within communication systems such as wireless and wire line voice and/or data communications. Packet transmission service has also been used in association with digital communication systems which permit the efficient allocation of system resources via any of the well known access schemes, such as, for example, Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA) or any combination thereof. As will be appreciated, system resources may comprise radio frequency spectrum divided into communication channels to facilitate the transmission of user information.
In a digital packet transmission system, there are several access procedures a requesting unit can initiate when attempting to obtain and utilize system resources. These access procedures inform the system which type of operation a requesting unit is attempting to perform. Such operations include but are not limited to, call origination, location reporting, registration and page response.
The typical access procedure may be summarized as follows. A requesting unit transmits a system access request (request) over a request channel to a communications controller, starts a retry timer, and awaits a bandwidth grant message from the controller, informing the unit when and which channel is available for use. If the communications controller fails to respond to the request before the retry timer expires, the requesting unit will reissue the request (duplicate request). This procedure will continue until the requesting unit either receives a valid assignment of a resource (bandwidth grant), reaches a maximum number of retries, or a packet lifetime timer expires, informing the requesting unit to cease.
In a TDMA system, several requests may be received by the controller per TDMA frame. These requests are stored in memory (queued) until time slots available to satisfy the requests are allocated. For identification purposes, each requesting unit's request contains identification information. Therefore, a communications controller receives specific information with which to distinguish one unit's access request from that of another. Requests, however, typically do not contain information permitting the controller to distinguish a requesting unit's requests one from another. Thus, whenever a requesting unit retransmits its request there is no means for the controller to determine whether the received request is the unit's first or a subsequent attempt. Accordingly, the above described scenario is extremely susceptible to the misallocation of system resources.
If the controller fails to respond to a requesting unit's initial request within the retry interval, the requesting unit will issue a duplicate request. Since the controller receives no information regarding the relationship of the duplicate request to other requests, the controller is unable to correlate the duplicate request with a request already in progress. This may result in the controller processing both requests and allocating duplicate resources for the same requesting unit. Since the requesting unit will respond to the first bandwidth grant received, all subsequent granted resources will go unused and result in a waste.
The occasional misallocation of such a resource is not catastrophic to system performance, since the unused resource will eventually be returned to service. However, the increased occurrence of misallocation, or misallocation during periods of heavy use presents a formidable obstacle to the efficient operation of a modern digital communication system. It would be extremely advantageous therefore to provide a method and apparatus for limiting the number of duplicate access requests transmitted by a remote unit in order to reduce request traffic contention and ultimately reduce the likelihood of resource misallocation in a digital communication system.